Free OS X Mavericks now powers half of all Macs

Successor likely to ship in October

OS X Mavericks powered half of all Macs that went online in March, the largest percentage of any individual version of Apple's operating system since 2009's Snow Leopard, statistics showed.

Mavericks, which carries the numerical designation of OS X 10.9, accounted for 49.5% of all Mac operating systems tracked by Web analytics company Net Applications last month. The six-month-old operating system gained about 4 percentage points in March, slightly more than the month before.

Its nearest rival for March was Snow Leopard, or OS X 10.6, which debuted in August 2009, and has resisted retreat better than its next two successors, Lion (OS X 10.7) and Mountain Lion (OS X 10.8), which launched in 2011 and 2012, respectively. Last month, Snow Leopard lost share at more than twice its 12-month average; the drop of almost 2 percentage points was the largest since August 2012, an indication that Snow Leopard-powered Macs' replacement or upgrade pace has quickened, perhaps because the OS has fallen off Apple's support list.

During their approximately one year each of being the newest version of OS X, neither Lion nor Mountain Lion reached the level of Mavericks last month. Lion topped out at 47% while Mountain Lion managed 49%.

Of the last four versions of OS X, only Snow Leopard, which was Apple's most current for nearly two years, exceeded a 50% "user share," the metric estimate that Net Applications publishes monthly.

Mavericks' dominance of the OS X rolls can be credited to Apple's 2013 decision to make it free to download and install by most Mac owners. In October 2013, Apple announced that Mavericks, as well as future operating system upgrades, would be given to customers free of charge.

Apple has not disclosed what it will name the next version, OS X 10.10, or when it will release the upgrade, but is expected to reveal the former at its annual Worldwide Developers Conference (WWDC), which will run June 2-6 in San Francisco.

If the company repeats last year's process, it will unveil OS X 10.10 at WWDC on June 2 and make a preview available to registered developers that same day. Although Apple could surprise customers -- and developers -- with an early launch of the upgrade, for the last three versions Apple has waited an average of 148 days between announcement and official release. Using that average and a June 2 announcement, OS X 10.10 would launch on Oct. 28.

Net Applications calculates operating system user share with data obtained from more than 160 million unique visitors who browse 40,000 Web sites that the company monitors for clients.

OS X Mavericks powered 50% of all Macs in March, the largest user share by a single edition since 2009's Snow Leopard. (Data: Net Applications.)